Modern computing devices (e.g., desktop computers, laptops, netbooks, tablets, smartphones, etc.) can generally operate in one of a plurality of power modes or power states. These power modes may range from a “Working” power mode, in which the computing device is fully powered and operational, to an “Off” power mode in which the device is fully powered down and non-operational. Traditionally this “Working” power mode is the default operating mode of computing devices. However, there are power modes in between these two power modes (Working and Off) that trade-off functionality for power savings or reduced power consumption.
For example, a low-power state of the computing device may be referred to as “Standby,” “Sleep,” or “Suspend to RAM” or “Suspend.” In such a low-power state, aside from powering the random access memory (“RAM”) that is required to restore the computing device's state, the computing device attempts to reduce or cut power to all unneeded parts of the machine (e.g., the hard disk(s) stop spinning, the display device is placed into a dark or low-power state, and peripheral devices are de-powered). Such a low-power state often is called Standby (for computing devices running a Microsoft Windows 95-Server 2003 operating system), or is called Sleep (for computing devices running an Apple operating system or a Windows Vista, Windows 7, Windows Server 2008 operating system), or Suspend (for computing devices running a Linux operating system). In such a state, the processing functions of the computing device are powered down, and some small amount of power is used to preserve the contents of RAM and support waking up the computing device from the low-power state into the normal or full power state. When the computing device is placed into the Standby, Sleep, or Suspend to RAM state, it typically consumes less than about 20% of the total power than is consumed with the device is in the normal or full power mode. In various systems this sleep power mode may also be referred to “standby,” “suspend,” “suspend-to-memory,” or Advanced Configuration and Power Interface (ACPI) power state S3.
Various other power states are known to exist. For example, a computing device may turn off or place in standby individual components or sub-systems of the computing device. Examples may include placing a monitor component in standby or an off power mode if there has been no user interaction after a predetermined period of time. In another example, a hard drive may be placed in standby, turned off, or “spun-down” if no access (e.g., reading or writing, etc.) has occurred to the hard drive for a preconfigured period of time. These component or sub-system standby power modes may be referred to as ACPI device power mode D1 or D2. The device off power mode may be referred to as ACPI device power mode D0. Various computing device architectures may employ other power mode schemes besides ACPI.